﻿#region License
// Copyright (c) 2007 James Newton-King
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
#endregion

using System;
using System.Text.RegularExpressions;
using Newtonsoft.Json.Bson;
using System.Globalization;
using Newtonsoft.Json.Serialization;

namespace Newtonsoft.Json.Converters
{
  /// <summary>
  /// Converts a <see cref="Regex"/> to and from JSON and BSON.
  /// </summary>
  public class RegexConverter : JsonConverter
  {
    private const string PatternName = "Pattern";
    private const string OptionsName = "Options";

    /// <summary>
    /// Writes the JSON representation of the object.
    /// </summary>
    /// <param name="writer">The <see cref="JsonWriter"/> to write to.</param>
    /// <param name="value">The value.</param>
    /// <param name="serializer">The calling serializer.</param>
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
      Regex regex = (Regex) value;

      BsonWriter bsonWriter = writer as BsonWriter;
      if (bsonWriter != null)
        WriteBson(bsonWriter, regex);
      else
        WriteJson(writer, regex, serializer);
    }

    private bool HasFlag(RegexOptions options, RegexOptions flag)
    {
      return ((options & flag) == flag);
    }

    private void WriteBson(BsonWriter writer, Regex regex)
    {
      // Regular expression - The first cstring is the regex pattern, the second
      // is the regex options string. Options are identified by characters, which 
      // must be stored in alphabetical order. Valid options are 'i' for case 
      // insensitive matching, 'm' for multiline matching, 'x' for verbose mode, 
      // 'l' to make \w, \W, etc. locale dependent, 's' for dotall mode 
      // ('.' matches everything), and 'u' to make \w, \W, etc. match unicode.

      string options = null;

      if (HasFlag(regex.Options, RegexOptions.IgnoreCase))
        options += "i";

      if (HasFlag(regex.Options, RegexOptions.Multiline))
        options += "m";

      if (HasFlag(regex.Options, RegexOptions.Singleline))
        options += "s";

      options += "u";

      if (HasFlag(regex.Options, RegexOptions.ExplicitCapture))
        options += "x";

      writer.WriteRegex(regex.ToString(), options);
    }

    private void WriteJson(JsonWriter writer, Regex regex, JsonSerializer serializer)
    {
      DefaultContractResolver resolver = serializer.ContractResolver as DefaultContractResolver;

      writer.WriteStartObject();
      writer.WritePropertyName((resolver != null) ? resolver.GetResolvedPropertyName(PatternName) : PatternName);
      writer.WriteValue(regex.ToString());
      writer.WritePropertyName((resolver != null) ? resolver.GetResolvedPropertyName(OptionsName) : OptionsName);
      serializer.Serialize(writer, regex.Options);
      writer.WriteEndObject();
    }

    /// <summary>
    /// Reads the JSON representation of the object.
    /// </summary>
    /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>
    /// <param name="objectType">Type of the object.</param>
    /// <param name="existingValue">The existing value of object being read.</param>
    /// <param name="serializer">The calling serializer.</param>
    /// <returns>The object value.</returns>
    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
      if (reader.TokenType == JsonToken.StartObject)
        return ReadRegexObject(reader, serializer);
      
      if (reader.TokenType == JsonToken.String)
        return ReadRegexString(reader);

      throw JsonSerializationException.Create(reader, "Unexpected token when reading Regex.");
    }

    private object ReadRegexString(JsonReader reader)
    {
      string regexText = (string)reader.Value;
      int patternOptionDelimiterIndex = regexText.LastIndexOf('/');

      string patternText = regexText.Substring(1, patternOptionDelimiterIndex - 1);
      string optionsText = regexText.Substring(patternOptionDelimiterIndex + 1);

      RegexOptions options = RegexOptions.None;
      foreach (char c in optionsText)
      {
        switch (c)
        {
          case 'i':
            options |= RegexOptions.IgnoreCase;
            break;
          case 'm':
            options |= RegexOptions.Multiline;
            break;
          case 's':
            options |= RegexOptions.Singleline;
            break;
          case 'x':
            options |= RegexOptions.ExplicitCapture;
            break;
        }
      }

      return new Regex(patternText, options);
    }

    private Regex ReadRegexObject(JsonReader reader, JsonSerializer serializer)
    {
      string pattern = null;
      RegexOptions? options = null;

      while (reader.Read())
      {
        switch (reader.TokenType)
        {
          case JsonToken.PropertyName:
            string propertyName = reader.Value.ToString();

            if (!reader.Read())
              throw JsonSerializationException.Create(reader, "Unexpected end when reading Regex.");

            if (string.Equals(propertyName, PatternName, StringComparison.OrdinalIgnoreCase))
              pattern = (string)reader.Value;
            else if (string.Equals(propertyName, OptionsName, StringComparison.OrdinalIgnoreCase))
              options = serializer.Deserialize<RegexOptions>(reader);
            else
              reader.Skip();
            break;
          case JsonToken.Comment:
            break;
          case JsonToken.EndObject:
            if (pattern == null)
              throw JsonSerializationException.Create(reader, "Error deserializing Regex. No pattern found.");

            return new Regex(pattern, options ?? RegexOptions.None);
        }
      }

      throw JsonSerializationException.Create(reader, "Unexpected end when reading Regex.");
    }

    /// <summary>
    /// Determines whether this instance can convert the specified object type.
    /// </summary>
    /// <param name="objectType">Type of the object.</param>
    /// <returns>
    /// 	<c>true</c> if this instance can convert the specified object type; otherwise, <c>false</c>.
    /// </returns>
    public override bool CanConvert(Type objectType)
    {
      return (objectType == typeof (Regex));
    }
  }
}